Organic electronic devices and in particular organic light-emitting devices (OLEDs) are commonly manufactured as a sequence of layers deposited on top of each other such as a first electrode on a supporting substrate, several organic and inorganic layers, and a second electrode. So far, OLED technology is lacking a high-resolution patterning method for RGB displays for small molecules. The deposition technologies developed for small molecules so far show limitations for mass production of large-sized displays.
Conventionally, vacuum evaporation is employed as the physical vapor deposition method in forming the organic layers. A common method for patterning of the organic layers e.g. for red, green, and blue emitting sub-pixels in a full-color display, is the shadow mask technique. However, this technique is limited in size, resolution of the panel, and the individual fill-factor of the pixel. For example, shadow mask technology becomes extremely complicated in particular for small feature sizes. The material deposition during the process requires regular mask cleaning steps which delay the manufacturing. Thermal expansion of the mask during the deposition limits the precision and aperture ratio. Moreover, repeatedly necessary mask alignment is time consuming and reduces yield.
A method used for patterning polymer light-emitting devices is ink-jet printing of dissolved polymers as described in U.S. Pat. No. 6,087,196. This method of dispensing a liquid solution is not suitable for multi-layer OLEDs based on small molecules because previously deposited layers are re-dissolved and intermixed by the sequential deposition of multiple layers from different solutions. When small molecules are heated some of the small molecules sublime directly, while others first melt and then evaporate. Therefore a new way of depositing such molecules is needed. It follows that there is still a need in the art for improved patterning of structures for the fabrication of semiconductor devices, sensors, biochips, and displays using organic and/or inorganic active or biological layers.